Field
Exemplary embodiments relate to a method for controlling a decoding process based on a path metric value, and, more particularly, to a method for terminating a decoding process of a control channel and reducing blind decoding overload based on a path metric value.
Discussion
A Long Term Evolution (LTE) system uses Physical Downlink Control Channel (PDCCH) as a format of downlink control channel. The downlink refers to a radio communication from a base station, such as an evolved NodeB (eNodeB), to a mobile device, such as a user equipment (UE) supporting a mobile communication, e.g., LTE standards technologies. The PDCCH includes Downlink Control Information (DCI), and various formats of DCIs transport control information for one or more UEs. In an LTE system, DCIs are encoded by tail biting convolutional code (TBCC).
A UE may use a Viterbi decoding algorithm to decode the received PDCCH by a blind decoding scheme. The blind decoding according to the Viterbi decoding algorithm typically includes more than one training operations followed by a maximum likelihood path finding and a trace back operation to determine information bits, which are the most likely bits transmitted from a transmitter. The determined information bits are checked by a Cyclic Redundancy Check (CRC) and the validity of the information bits are determined based on the CRC check result.
In the blind decoding of an LTE system, control channel element (CCE) number and the aggregation level corresponding to the encoded data are unknown. Thus, the blind decoder, such as the Viterbi decoder, determines various possible sets of PDCCH data (“possible candidates”) determined according to various aggregation levels and possible CCE numbers, etc. The possible sets of PDCCH data determined from the received data mapped in certain common search space and UE-specific search space are candidates for the blind decoding. The number of blinding decoding operations may vary according to the number of aggregation level and the number of carriers. In an LTE system, the number of blind decoding attempts is great and many blind decoding attempts yield useless results because incorrectly assumed parameters, such as an incorrect aggregation level, were applied. For these incorrect decoding attempts, the decoder wastes significant time and battery power. Accordingly, this blind decoding process is inefficient in terms of the decoding speed and power consumption.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the inventive concept, and, therefore, it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art.